<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style type="text/css">


    </style>

</head>
<body>
<!--边距合并 取最大值，两个div之间的距离就是20px-->
<div style="border: 1px solid red;margin-bottom: 20px">
    nihao a
</div>
<div style="border: 1px solid red;margin-top: 10px;display: none;" id="div1" onmouseover="">
    nihao a
</div>
</body>
<script type="application/javascript" style="style">
    var dive=document.getElementById("div1");
    function change(){
        dive.sty
    }

</script>
</html>